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openGauss每日一练第 6 天

原创 陶笑 2022-11-29
598

学习目标

学习openGauss体系结构,通过实验,了解用户一次只能连接到一个数据库,没法访问其他数据库的对象。(注:本实验没有使用dblink插件)

课后作业

1.创建用户user1,分别在数据库musicdb1、数据库musicdb2创建表t11,t21

--创建用户 musicdb=# create user user1 identified by 'taox1110!'; CREATE ROLE openGauss=# ALTER USER user1 SYSADMIN; ALTER ROLE openGauss=# \c musicdb1 user1 Password for user user1: Non-SSL connection (SSL connection is recommended when requiring high-security) You are now connected to database "musicdb1" as user "user1". --在db1库创建测试表T11 musicdb1=> create table t11(col1 char(20)); CREATE TABLE musicdb1=> insert into t11 values('Hello openGauss! 11'); INSERT 0 1 musicdb1=> select * from t11; col1 ---------------------- Hello openGauss! 11 (1 row)
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--连接db2库,并创建测试表t12 musicdb1=> \c musicdb2 user1 Password for user user1: Non-SSL connection (SSL connection is recommended when requiring high-security) You are now connected to database "musicdb2" as user "user1". musicdb2=> create table t12(col1 char(20)); CREATE TABLE musicdb2=> insert into t12 values('Hello openGauss! 12'); INSERT 0 1 musicdb2=> select * from t12; col1 ---------------------- Hello openGauss! 12 (1 row)
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2.user1用户连接到数据库musicdb1,并访问数据库musicdb1下的表t11

openGauss=# \c musicdb1 user1 Password for user user1: Non-SSL connection (SSL connection is recommended when requiring high-security) You are now connected to database "musicdb1" as user "user1". musicdb1=> select * from t11; col1 ---------------------- Hello openGauss! 11 (1 row)
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3.在这个连接中(使用数据库用户user1连接到数据库musicdb1)访问数据库musicdb2下的t21表(会报错)

--og跨库访问显然是不行的,这个和mysql不一样,pg是强隔离,而mysql是弱隔离 musicdb2=> \c musicdb1 user1 Password for user user1: Non-SSL connection (SSL connection is recommended when requiring high-security) You are now connected to database "musicdb1" as user "user1". musicdb1=> select * from musicdb1.public.t11; col1 ---------------------- Hello openGauss! 11 (1 row) musicdb1=> select * from musicdb2.public.t12; ERROR: cross-database references are not implemented: "musicdb2.public.t12" LINE 1: select * from musicdb2.public.t12; ^
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4.使用数据库用户user1连接到数据库musicdb2,访问数据库musicdb2下的t21表。

musicdb1=> \c musicdb2 user1 Password for user user1: Non-SSL connection (SSL connection is recommended when requiring high-security) You are now connected to database "musicdb2" as user "user1". musicdb2=> select * from musicdb2.public.t12;; col1 ---------------------- Hello openGauss! 12 (1 row)
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墨天轮-雪宝君
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作业审核合格,一起参与21天openGauss学习打卡活动! 活动详情:https://www.modb.pro/db/551619
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